Flywheel shaving and alternators

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Nathan2115

Nathan2115

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The placement of the engine, a briggs and stratton 3hp on my bike (see profile for build thread) is such that my leg will get ripped to shreds by the cooling fins on the flywheel. Can i machine these fins off without affecting the balancing and stabilizing nature of the flywheel, and if i can, how far can i go?

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And about an alternator: i would like to have a headlight. Will magneto alternators off ebay work paired with a small battery?

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Why not just use a small battery on its own? If you want 12V lights, I use them with lithium ion battery packs meant for security cameras and accent lights. I have a 30W LED H7 bulb in a car headlight that runs for 3.5 hours on what's claimed to be a 6000mAh pack and a trailer brake light that was at 12 hours on a claimed 3000mAh pack before I gave up on timing it.
 
Duchess said:
Why not just use a small battery on its own? If you want 12V lights, I use them with lithium ion battery packs meant for security cameras and accent lights. I have a 30W LED H7 bulb in a car headlight that runs for 3.5 hours on what's claimed to be a 6000mAh pack and a trailer brake light that was at 12 hours on a claimed 3000mAh pack before I gave up on timing it.
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Thanks for responding. I would like the bike to be self sufficient. Having a battery wouldn't be an issue, I'm just exploring options.
 
For the generator, do you mean the bottle-type magnetos usually called dynamos that are used for lighting on bicycles? You can definitely use them and you wouldn't need a battery if you get modern lighting made for bicycle generators as they have capacitors to maintain lighting at a stop.

As for the cooling fins on the flywheel, I don't know. Reduced cooling question aside, I would imagine that if you had a way to balance the flywheel, you could machine the fins off completely and either drill holes or add small weights to balance it out after, but that's just a guess on my part.
 
Duchess said:
For the generator, do you mean the bottle-type magnetos usually called dynamos that are used for lighting on bicycles? You can definitely use them and you wouldn't need a battery if you get modern lighting made for bicycle generators as they have capacitors to maintain lighting at a stop.

As for the cooling fins on the flywheel, I don't know. Reduced cooling question aside, I would imagine that if you had a way to balance the flywheel, you could machine the fins off completely and either drill holes or add small weights to balance it out after, but that's just a guess on my part.
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Awesome. Ill pick up a dynamo. Great idea for the balancing. I guess i'll weigh the engine before and after removing the cooling fins to find out the weight of the fins, then add weights to the flywheel as you described to compensate for balance.

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I don't know how finicky a briggs is going to be about balance, but...if your going to balance the flywheel. You need to find the heavy spots and either remove weight, or add weight opposite, to balance it. It proved difficult to type up a description of how to make your own balancing stand...so, just search for motorcycle wheel balancer or flyweel balancer and you will get the idea. The ones I saw all showed two mounted bearings per side with the axle riding on top...you only need one precision bearing per side ON the axle...and have the bearings rest in the square tubing of the stand...cheap and easy.

If your just shaving the fins (assuming machining)...that really shouldn't effect the balance. If you are removing them in a more improvised way (hacking :bigsmile:)...then all bets are off.

As to cooling, I don't know. I would assume you would be good as long as you don't let it run static for lengthy periods.

Jason
 
RustyGold said:
I don't know how finicky a briggs is going to be about balance, but...if your going to balance the flywheel. You need to find the heavy spots and either remove weight, or add weight opposite, to balance it. It proved difficult to type up a description of how to make your own balancing stand...so, just search for motorcycle wheel balancer or flyweel balancer and you will get the idea. The ones I saw all showed two mounted bearings per side with the axle riding on top...you only need one precision bearing per side ON the axle...and have the bearings rest in the square tubing of the stand...cheap and easy.

If your just shaving the fins (assuming machining)...that really shouldn't effect the balance. If you are removing them in a more improvised way (hacking :bigsmile:)...then all bets are off.

As to cooling, I don't know. I would assume you would be good as long as you don't let it run static for lengthy periods.

Jason
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Thanks for the advice.

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Oh...I assumed the briggs is internally balanced. I'm sure there is a forum somewhere on the internerd that has such info. If externally balanced, you would have to match the imbalance that exists on the flywheel before removing the fins :).

Jason
 
Nathan2115 said:
The placement of the engine, a briggs and stratton 3hp on my bike (see profile for build thread) is such that my leg will get ripped to shreds by the cooling fins on the flywheel. Can i machine these fins off without affecting the balancing and stabilizing nature of the flywheel, and if i can, how far can i go?

Sent from my SM-G920P using Tapatalk
Click to expand...
I machined the fins down approximately 3/8 of on inch on a milling machine. This was on a 300cc Kawasaki single snowmobile engine that ran at 5000 rpm. No ill effects for many years running. Never balanced it. But, I machined it as precisely as I could. I didn't want to use lathe because I thought I would deform or crack fins with the interrupted cut. At the rpm's Brigg's run you could probably do the same I'm guessing.
 

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